The purpose of this project is to explore short and long term effects of steroids on the cardiovascular tissues. Methodology consists of administering steroids to animals and then studying the ultrastructural modifications by scanning and transmission electron microscopy. Bibliographic references: Albert, E.N. and Nayak, R.K. Surface topography of vena cava as observed with the scanning electron microscope. Submitted to Am. J. Anat., 1975.